[PATCH 1/3] iommu: Provide iommu_probe_device_locked()

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The two callers coming from bus_tye -> dma_configure() already have the
device_lock held for the device being probed. Mark this in the API so that
the core code doesn't attempt to re-acquire the same lock and deadlock.

  __iommu_probe_device from iommu_probe_device+0x10/0x40
  iommu_probe_device from of_iommu_configure+0xf8/0x1c8
  of_iommu_configure from of_dma_configure_id+0x188/0x450
  of_dma_configure_id from platform_dma_configure+0x24/0x60
  platform_dma_configure from really_probe+0xac/0x3d4
  really_probe from __driver_probe_device+0xa0/0x1e8
  __driver_probe_device from driver_probe_device+0x30/0xd0
  driver_probe_device from __driver_attach+0x10c/0x190
  __driver_attach from bus_for_each_dev+0x60/0xb4
  bus_for_each_dev from bus_add_driver+0xe0/0x208
  bus_add_driver from driver_register+0x7c/0x118
  driver_register from exynos_drm_init+0xe0/0x14c
  exynos_drm_init from do_one_initcall+0x6c/0x318
  do_one_initcall from kernel_init_freeable+0x1c4/0x214
  kernel_init_freeable from kernel_init+0x18/0x12c
  kernel_init from ret_from_fork+0x14/0x2c

Internally make __iommu_probe_device() require the caller to get the
device_lock().

The three remaining callers of iommu_probe_device() don't seem to hold the
device_lock():

 powerpc/kernel/iommu.c: iommu_add_device()
 iommu/iommu.c: iommu_bus_notifier()/BUS_NOTIFY_ADD_DEVICE/
 intel/iommu.c: probe_acpi_namespace_devices()

Fixes: a2dde836050f ("iommu: Complete the locking for dev->iommu_group")
Reported-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
Closes: https://lore.kernel.org/linux-iommu/bc5d6aa8-e8ca-c896-2f39-af074d55e436@xxxxxxxxxxx
Tested-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
---
 drivers/acpi/scan.c      |  5 +++--
 drivers/iommu/iommu.c    | 34 ++++++++++++++++++++++------------
 drivers/iommu/of_iommu.c |  2 +-
 include/linux/iommu.h    |  1 +
 4 files changed, 27 insertions(+), 15 deletions(-)

diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
index daa64dd687524b..3771164af60279 100644
--- a/drivers/acpi/scan.c
+++ b/drivers/acpi/scan.c
@@ -1579,10 +1579,11 @@ static const struct iommu_ops *acpi_iommu_configure_id(struct device *dev,
 
 	/*
 	 * If we have reason to believe the IOMMU driver missed the initial
-	 * iommu_probe_device() call for dev, replay it to get things in order.
+	 * iommu_probe_device_locked() call for dev, replay it to get things in
+	 * order.
 	 */
 	if (!err && dev->bus)
-		err = iommu_probe_device(dev);
+		err = iommu_probe_device_locked(dev);
 
 	/* Ignore all other errors apart from EPROBE_DEFER */
 	if (err == -EPROBE_DEFER) {
diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 25d7327e8013e7..ecf61bd3cfb076 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -452,24 +452,23 @@ static int __iommu_probe_device(struct device *dev, struct list_head *group_list
 	struct group_device *gdev;
 	int ret;
 
-	if (!ops)
-		return -ENODEV;
 	/*
 	 * Allow __iommu_probe_device() to be safely called in parallel,
 	 * both dev->iommu_group and the initial setup of dev->iommu are
 	 * protected this way.
 	 */
-	device_lock(dev);
+	device_lock_assert(dev);
+
+	if (!ops)
+		return -ENODEV;
 
 	/* Device is probed already if in a group */
-	if (dev->iommu_group) {
-		ret = 0;
-		goto out_unlock;
-	}
+	if (dev->iommu_group)
+		return 0;
 
 	ret = iommu_init_device(dev, ops);
 	if (ret)
-		goto out_unlock;
+		return ret;
 
 	group = dev->iommu_group;
 	gdev = iommu_group_alloc_device(group, dev);
@@ -505,7 +504,6 @@ static int __iommu_probe_device(struct device *dev, struct list_head *group_list
 			list_add_tail(&group->entry, group_list);
 	}
 	mutex_unlock(&group->mutex);
-	device_unlock(dev);
 
 	if (dev_is_pci(dev))
 		iommu_dma_set_pci_32bit_workaround(dev);
@@ -519,16 +517,16 @@ static int __iommu_probe_device(struct device *dev, struct list_head *group_list
 	iommu_deinit_device(dev);
 	mutex_unlock(&group->mutex);
 	iommu_group_put(group);
-out_unlock:
-	device_unlock(dev);
 	return ret;
 }
 
-int iommu_probe_device(struct device *dev)
+int iommu_probe_device_locked(struct device *dev)
 {
 	const struct iommu_ops *ops;
 	int ret;
 
+	device_lock_assert(dev);
+
 	ret = __iommu_probe_device(dev, NULL);
 	if (ret)
 		return ret;
@@ -540,6 +538,16 @@ int iommu_probe_device(struct device *dev)
 	return 0;
 }
 
+int iommu_probe_device(struct device *dev)
+{
+	int ret;
+
+	device_lock(dev);
+	ret = iommu_probe_device_locked(dev);
+	device_unlock(dev);
+	return ret;
+}
+
 static void __iommu_group_free_device(struct iommu_group *group,
 				      struct group_device *grp_dev)
 {
@@ -1789,7 +1797,9 @@ static int probe_iommu_group(struct device *dev, void *data)
 	struct list_head *group_list = data;
 	int ret;
 
+	device_lock(dev);
 	ret = __iommu_probe_device(dev, group_list);
+	device_unlock(dev);
 	if (ret == -ENODEV)
 		ret = 0;
 
diff --git a/drivers/iommu/of_iommu.c b/drivers/iommu/of_iommu.c
index 157b286e36bf3a..b5b7d4bd2cefb9 100644
--- a/drivers/iommu/of_iommu.c
+++ b/drivers/iommu/of_iommu.c
@@ -160,7 +160,7 @@ const struct iommu_ops *of_iommu_configure(struct device *dev,
 	 * probe for dev, replay it to get things in order.
 	 */
 	if (!err && dev->bus)
-		err = iommu_probe_device(dev);
+		err = iommu_probe_device_locked(dev);
 
 	/* Ignore all other errors apart from EPROBE_DEFER */
 	if (err == -EPROBE_DEFER) {
diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index f1e18e81fca78b..cb4fc518797039 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -709,6 +709,7 @@ static inline void dev_iommu_priv_set(struct device *dev, void *priv)
 }
 
 int iommu_probe_device(struct device *dev);
+int iommu_probe_device_locked(struct device *dev);
 
 int iommu_dev_enable_feature(struct device *dev, enum iommu_dev_features f);
 int iommu_dev_disable_feature(struct device *dev, enum iommu_dev_features f);
-- 
2.41.0




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